It will focus on individuals at high risk of HIV infection with services aiming to prevent the spread of the disease and improve care and treatment of those infected by HIV, an embassy statement said.
The Khmer HIV/AIDS NGO Alliance (Khana) will lead a consortium of organisations at the forefront in the fight against HIV/AIDS in Cambodia, it said.
PSI and FHI360, international NGOs known for their innovation in the global fight against AIDS, will join Khana to help strengthen Cambodia's HIV/AIDS response.
"The US is Cambodia's steadfast partner in the fight against HIV/AIDS," said US Ambassador William E. Todd at a ceremony to announce the launch in Siem Reap province.
The US is Cambodia's largest bilateral health donor, providing approximately 20 percent of all resources behind its national HIV/AIDS programme, the statement said.
According to Cambodia's National institute of Public Health, currently 77,861 Cambodian people have contracted HIV/AIDS that includes 5,349 children.
The disease killed about 2,365 people in the country last year.